docs: def datefmt_to_regex(datefmt):
      """
      Convert a strftime format string to a regex.
  
      :param datefmt: strftime format string
      :type datefmt: ``str``
  
      :returns: Equivalent regex
      :rtype: ``re.compite``
      """
      new_string = datefmt
      for pat, reg in PATTERN_MATCHNG:
          new_string = new_string.replace(pat, reg)
      return re.compile(r'(%s)' % new_string)